Cupola furnace



CUPOLA FURNACE Filed May 15, 1952 4 Sheets Sheet 1 ,9 :J-Z I 2 ""9INVENTOR.

- ROBERT m" R. DOAT CUPOLA FURNACE Feb. 16, 1954 4 Sheets-Sheet 2 FiiedMay 15, 1952 Feb. 16, 1954 R. DOAT 2,669,446

' CUE-OLA FURNACE Filed May 15, 1952 4 Sheets-Sheet s 'INVENTOR. 1 75.4. ROBERT R. DOAT CUPOLA FURNACE Feb. 16, 1954 4 Sheets-$heet 4 FiledMay 15, 1952 S I J 2 INVENTOR.

ROBERT DOAT Patented Feb. 16, 1954 "12Claims. )1 ,The -,presentinvention relates to .oupola ,furnacestand; processeshfor. oper ting;vthe; same UMOI'B particularly the ,present invention ,reilates .to ,acupola .furnace which is a a ed to Junction raise-as a as producer.

-,This .tap plication ,is a-tcontinuation-in-part oi ;U.,-,s.;patentapplication. SerialNo. 165,420, ,filed June 1, 1950, and entitledProcess FoinMelting -,-Meta l=. Qressand Cupola ,-,Furnace -Therefor,now abandoned.

,lmzconuentionaltcupola iurnaoes it istaiairly .diificult -matter to@produc .a uniform produ -of: hi h-quality. :Ehereasonsior thisare,among others, that, intatternpting ,to. conserve fuel there exists ,-.in:the ffulnace tan oxidizing atmosphere which iresults sin oxidation 60f"various elements in the charge so that an inferior product is produced.:Moreover, beoauseqofzathis oxidation and beeause ofzsmixingmof :the;slag.s,ioath=,, with the materials of the refractory lining, it ii5impossible accurately control the-slag through whichtthe .molten metalpasses.

vBecause the ;operator is not* the master of the molten slag within the"furnace; he cannot con- ,trolthe p oduct produced. The reasongfor this,is that the .molt n .metal pass n "throu h the slag bath reacts withthe slag bath, and this re- .ectionis uncontrollable-when th slagitself.cannot be,accuratelyr,controlled.

Another disadvantage of conventional 501lpolas tha they vcannot =b tonrated ;continuously forzlons rheriodswrofutime :hecause th reifractorylining rdeteriorates :rapidlymand itxthus becomes 1 necessary .tointerrupt the :operations and repair thellining. "For example-withaeconventional cupola which has an output of 20 tons of molten metal anhour, it is seldom possibleto exceed 1 hours of --continuous operation.hfter this time-"it" is-"necessary to repair the refractory kliningvaboveand below'i the melting zone.

This conventional type ofgcupola, which may be :used either, in an, ironor steelfoun'dry, is gen- "erally, provided with one ,ortwo ranges ofrec- :tangulartuyeres. The-ratio between 171181101izontal cross-sectionof the interior ,of the eupola and :the sum of the crossrsections ofthetuyeres varies betweenfi and 12. The air pres- .sure. at. thetuyeres isgenerally" lowpheing' inithe cupola has a calorific content helowZOO-calories per cubic meter andetheratio of C0 to J 002 in this gas--is g from *054 *to 0:6. The molten metal produced is-more or; lessoxidized and the silicon 'lossfrom the charge varies "from--to'-15 1;Many inventors have trie'd to modify ,sucnan .in .o de t av id thedisadvanta s thereof. There have been .satteinpts to change the mountingof the tuyeres. .Afhotblast under ptessunehasbeen u draasuee e h Mo of.the ,U. 5 S. ,A. and also ,hy ,Piwowarsky, in ,Eurone.

Theremasybeemd v lone mtth Aha d wice :for icontinually tmelt a 11in=.o1rde rte aveid :lfitfippageyflfit'hez openings.iandimoretrecentlyzthe silicious refractory linings have been replacedhy basic refractory linings. i Pi wonwarskyl hasrpro- 'posed a cupolaim-which a y'part of the coke is burned in a separate chamber'i n'such away that-all of thecarhon may be converted into" E0 When a hot blastisusedin such 1cupo1as, -it1is U possible t0 iminish the loss of siliconbut the w a and deterioration of th 1 inin i ..acqe1- erated as a resultof the higher temperatures i'Whi-Ch; pr.evai1., i-n t e re ion of thetuye w themesultthat-the operation neqessar wemains inte mittent.

. nzaspitei f thens sofi hotaairit th tm lt nazconibmllesr'to :take;place iman oxidizine=aatmosph r gfheslagthas a ratioofvOaOtowSiGzwhichvis;

than L 1,- an'd it contains: a fairly largetamountqof iron oxidewhich-renders I the slag very fusible. Thespeed-of *gas-*flowing-=through these conven- -tiona1 eupolas i is very great-because of the-1rely) atively small size of these cupolas with respect tothehourlytonnage melted. The temperature of the gas at the outlet of suchconventional cu- ;polasyis generally-quite high,;being in the neigh- 59generally contains" less than 1'2 7% ,6 of :00.

All systems employed up to the present time are characterized by thefact that the fusion of the charge is unfortunately accompanied by tworegrettable phenomena:

1. The oxidation of part of the metallic elements of the charge:

2. The fusion and resulting deterioration of the refractory lining.

These oxidized elements and the molten material of the refractory liningdescend with the molten metal and become joined in the slag with neutralelements of the charge, with the result that the operator is not themaster of the composition of the slag, as was pointed out above. Severalauthorities, such as G. Somigli and E. Wittem have regretted this fact.For example, R. Perrin has stated that in a steel foundry the nature ofthe refractory lining used plays a preponderant and automatic role inthe quality of the product obtained because of the nature of the slagwhich is necessarily greatly affected by the material of the refractorylining.

One of the objects of the present invention is to overcome all of theabove serious disadvantages by maintaining a reducing atmosphere withinthe cupola.

Another object of the present invention is to greatly retard thedeterioration of the refractory lining so that the composition of theslag may be controlled in accordance with the material charged into thecupola.

A further object of the present invention is to provide a cupola whichis capable of maintaining therein a slag bath of constant depth.

Still another object of the present invention is to provide a means forgranulating the slag after it leaves the cupola.

Yet another object of the present invention is to provide a cupolafurnace which may also function as a gas producer.

A still further object of the present invention is to provide a cupolafurnace capable of producing in a continuous manner a high qualityproduct of constant composition and which may be varied by variation ofthe compositions of the charge.

An additional object of the present invention is to prevent setting ofthe slag while it is associated with the cupola.

Still another object of the present invention is to provide a means fordraining all molten metal and slag from a cupola when the latter is tobe used as a gas producer without stopping up the normal outlet for themolten metal of the cupola.

With the above objects in view the present invention mainly consists ofproviding a cupola furnace which has an elongated hollow body having avertical central axis and a bottom wall toward which molten metal andslag move. This hollow body is provided with an inner refractory liningand has a side wall portion adjacent the bottom wall thereof formed witha pair of openings one of which passes through the side wall portionsubstantially at the level of the bottom wall to lead molten metal fromthe hollow body and the other of which passes through the side wallportion above this one opening to lead slag from the hollow body. Areceiving chamber is connected to the hollow bodytat the side wallportion thereof and communicates with these openings, this receivingchamber having a slag discharge spout and a metal discharge spoutlocated below the slag discharge spout. The receiving chamber has across-sectional area in a horizontal plane which is substantiallysmaller than the cross-sectional area of the interior of the hollow bodyin the same horizontal plane, and the receiving chamber is also providedwith a dividing wall extending beneath the lower of the above-mentionedopenings and being located between the spouts to separate molten metaland slag from each other. A cooling means is provided to cool the entireouter surface of the hollow body and a gas outlet valve is located atthe top of the cupola to maintain the gas pressure therein at apredetermined value so as to maintain a slag bath of predeterminedconstant depth in the cupola.

With these objects also in view, the present invention mainly comprisesmeans for introducing hot air into a cupola furnace containing an excessof carbon in the charge so as to oxidize said carbon by introduction ofsaid hot air and thus raise the temperature in said cupola furnace andheat the charge therein while maintaining a reducing atmosphere in saidcupola furnace, thus melting the metallic oxides in said charge andreducing the same to the corresponding metal; and maintaining in saidcupola furnace a slag bath of constant depth through which said moltenmetal passes so as to cause said metal to react with said slag bathunder uniform onditions, thereby obtaining a metal having uniformproperties.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, as to its construction, together withadditional objects and advantages thereof, will be best understood fromthe following description of specific embodiments when read inconnection with the accompanying drawings, in which:

Fig. 1 is an elevational view of a furnace con structed in accordancewith the present invention and with parts thereof shown in section, Fig.1 being taken along line ii of Fig. 3 in the direction of the arrows;

Fig. 2 is a front elevation of the lower part of the cupola of Fig. 1,taken along line 2-2 of Fig. 3 in the direction of the arrows;

Fig. 3 is a plan view of the cupola of Fig. 1 taken along line 33 ofFig. 1 in the direction of the arrows;

Fig. 4 is a fragmentary sectional elevation taken along a centraldiameter of the lower part of the cupola;

Fig. 5 is a sectional view taken along line 5-5 of Fig. 4 in thedirection of the arrows;

Fig. 6 is a sectional view taken along line 6-6 of Fig. 5 in thedirection of the arrows;

Fig. 7 is a side elevation of a part of the furnace as seen from theright hand side of Fig. 2; and

Fig. 8 is an elevational view of a detail of the cupola illustrated inthe above figures.

Referring now to the drawings, it is seen that the cupola of the presentinvention is provided with a refractory lining l. Although it ispossible to provide the disclosed cupola with various refractorylinings, it is preferred to provide the same with a novel refractorylining capable of being applied in situ or capable of being made intobricks which can then be mounted in the interior of the furnace. I

Up to the present day it has been necessary e ceegcie to providerefractory "linings having diiierent "compositions depending upon theuses ior which they were "intended. In order to provide *a re-"fractory-lining which niightbe suitable for vari-#ousdiffereritusesxseveral compositions have been "proposed, but thesecompositions "either have an feirtremely low carbon content or no carbonat all.

*It is 11 therefore another object of the 'present invention toprovide anovel refractory 'lining which is ,"particularly suitable "for -"cupolafur- ".naces.

Iti's an"additional'objectof thepresent inventionto provideaprocess iorformin'g such novel refractory lining in "a cup'dla "furnace.

"With the "above objects in view the present rinverltion mainly"comprises refractory lining "essentially consis'ting of "finely dividedparticles of *'carbon,'-si1ica, alumina ferric oxide, calcium oxide "andmagnesia.

According to the preferred embodiment, the *finely dividedfp'articleshave a size of less than ':'5 7mm. and are E present in the proportionof "1 lpart ca'rbon'to "1 34-127 parts silica, OIO'Y Ogllpart alumina,01007 0023 part *ferric oxide, "01003- $010.12 part "calcium "oxide and020010 00035 "pa-rt magnesia. 'JIheterms fpart and parts as used in "the"specification. and claims refer'to the molecular? ratio entiresubstances to each other. ""The'ratioof'each "of*'the"substances of'therefractory lining .to each other is by molecules irather .thanby'weight.

.The "processffor producing the refractory lining according "to ,the 1present invention mainly ..lc omprises the steps .of homogeneouslymixing ."finly divided; particles of carbon, silica, alumina, .Iferricoxide, calciumoiiide and magnesia, "heatling the thus formedhomogeneous 1. mixture on- 'der pressure so as to form a substantiallysolid imassof thefinely divided,particles,"th:ereby obltaining a.re'fractorylining for furnaces.

In the, past refractory linings subjected to 'extreme conditions, asmuch thermochemical as .mechanical, presented the inconvenience of re-.quiring .Idiiierent r compositions for .x'cliffere'nt j purj. posesfforwhich the'lining was intended; an-

other inconvenience was the frequent necessity o'fstoppingl'theoperation o'fthe "furnacein'order .to repairthe liningflwhich waspartiallyidestroyed .at the Ilriigh temperatures of "operation 'oflthe.lfurnace. TfIliis .wasflparticularly the casewith Ihoti blast .cupolas.

variousidiiferenti compositions" have been progposed .to ..remedy theseinconveniences. These -.compositions contain .either no'cai'bon *atall'or 'veryllittle .carbon. .Occasionally bricks forming .thesefliningswere.placedona bed of bricks made of ,l practically pure carbon. (Thefollowing table indicates. the usual. composition of refractorylinings.which.do not contain carbon:

One ot the characteristics of the present I in- "'-vention is theuniting in the same -refra'ctory "composition 'of acarbonlwith the'substancesllisted 'ab'ove.

One can thus prepare a lining Capab1B' 'df*Iie-' 'si'sting extremelyhigh temperatures as well was being capable of resisting acid and-basicslag-s. "These linings are *particul arly suitable i for "metallurgicalcupolas utili'zing hot air, -the exterior 0'f 'which furnace is cooledand'wh-ich *cupblas can function I also* as a *gas "producer.

The novel lining used :in the *cupola "of the present invention uniteswith the "conventional "elements in such refractory-linings apredetermined -quantity of carbon. The novel lining 'is produced bycombining with "carbon, in z a pro determined molecular" proportion,other elements "which are noi'mally used in refractory linings suchas'SiOz, AlzOa Fez'OsyCaQ and -Mg'O. -All "of these elements=-areground, milled, pulverized or"crush-ed until their grains-have a size ofiess "than about *5 mm. A mixture 'is "then iormed from these elements,in such quantities that after -"olrying they will be in the refractoryilining in the following moiecular proportions:

7A characteristic of this novellining "is that afterdrying the molecularratio of S102 *toAliOa lie between 12 and 25. "To this mixture "thusobtained, only 'suiiicient water is addedto form'a coherent mass, thisquantity of water being in the vicinity of 4-.-8% by weightxof .themixture.

'With such a lining it is possible for acupolarto .Itis thus, possibleto convenientlyline in situ .or.with thehelpof bricks of the aboveindicated composition the crucible of the cupola furnaces. The. use ofthey lining according'to the present invention is particularlyadvantageousin the "case offhotlblast cupolas where the'thickness of thelining .isless than 150mm, .the lining being .utilized to the exclusionof anyotherauxiliary Illining.

With the use of the refractoryilining according to the present inventionmetallurgical cupolas havinga continuous flowing of basic slag canfunction for very long. periods of time 'without Linterruption.Oficoursathe lining maybe employedfor'other fusion apparatus, orforlfillingpocketsin the lining through whichthe slag "flows. .Itis alsopossible to obtain, bybriquetting .under pressure, any desired shape .orfform [of refractory bricks which can be"heated..loy any means.toll300C. or more.

In all cases, the lining presentsthe advantage of permitting utilizationof apparatus lined itherewith'fora long period "of .time without .de-'terioration'oithe lining and without the necessity "of repairingfissures therein. Therefore, suchliningsare particularly advantageous'for "cupolas according to the present invention.

The proportions-givenabove for the refrac- "tory lining accordingto thepresent invention'are thepreferredproportions*and it is possible *todev-iate considerably from "the: amounts without greatly diminishing theproperties of the refractory lining. The cupola is provided with a topwhich normally remains closed, although it is provided with a suitableconduit for carrying away gas, and this conduit is provided, as shown inFig. 1, with a valve 4 adjacent the top of the cupola to cupola tomaintain a constant gas pressure therein. This valve can also be locatedat some distance below the top, if desired. This gas pressure, producedby the air entering through the tuyeres and reacting with the charge inthe cupola, completely controls the thickness of the slag bath, as hasbeen proved by experiment. Increasing or decreasing the charge onlyincreases or decreases the rate of slag and metal flow and has no effecton the depth of the slag bath. The charge is placed in the cupolathrough a pair of doors overlying each other at the top of the cupola,and these doors are never opened simultaneously during operation of thecupola, so that the cupola top is always closed except for the gasoutlet valve.

As is shown in Fig. 2, the cupola is provided, not far from its bottom,with a plurality of tuyeres which are slidably mounted in cylindricalopenings 56, respectively, for axial movement so that the tuyeres may beadjusted with the outlet ends thereof located at a predetermineddistance from the inner lining l.

wardly beyond the inner lining I, the tuyeres provide, in theirhorizontal plane, a concentrated area of combustion which is spaced fromthe refractory lining so as to greatly retard deterioration thereof. Hotair is supplied to the furnace through the tuyeres 5| by means of pipes52 connected to a common air supply which is heated with the hot gasderived from the cupola. The

tuyeres 5! are sealed with respect to the openings 56 and the pipes 52by means of cords of asbestos 53, which enable the tuyeres to be shapedconically, as illustrated, so as to act as nozzles. By moving thetuyeres in the openings 50 it is possible to expand or contract theconcentrated combustion area located therebetween. The tuyres 51 arehollow, as clearly shown in Fig. 2, and they are connected with inletand outlet pipes for circulating cooling fluid through the tuyeres.These inlet and outlet pipes preferably communicate with a tank, or thelike (not shown), located above the tuyeres so that the fluid therein isunder a certain pressure which assures that the tuyeres will always befilled with the cooling fluid.

As is shown in Fig. 4, the bottom wall 2 of the cupola is inclined. Apair of opposite discharge openings 3 and A are respectively located onopposite sides of the cupola passing through the side walls thereof, theopening 3 being horizontal and located at the highest level of theinclined floor 2, whereas the opening 4 is horizontal and located at thelowest level of the inclined floor 2. When the cupola operates as afurnace for producing molten metal, the opening 4 is plugged and themolten metal flows out through the opening 3 into an outer receivingchamber 55. Ihis opening 3 is fairly long and of a fairly small diameterso that it might become plugged if a special means'were not provided toprevent this. Due to its small size and fairly long length, the opening3 is difficult to unstop. When the melting operations are interrupted,there will always remain within the cupola a residual amount of metaland slag which would plug up the opening By arranging v the tuyres sothat their inner ends extend in- 3 were it not for the inclined floor 2leading down to the discharge opening 4. This latter opening isperiodically opened when the melting is interrupted, as for example whenthe cupola is switched over from use as a melting furnace to use as agas producer, and the residual molten metal and slag which run outthrough the opening 4 enables the opening 3 to be maintained clear sothat it is almost never necessary to unplug the opening 3.

As is clearly shown in Fig. 4, an inclined opening 5 is provided abovethe opening 3. Molten metal flows from the interior of the cupolathrough the opening 3 and down the inclined floor 36 of the receivingchamber 55. Slag flows from the interior of the cupola body through theinclined opening 5 to the interior of the chamber 55 and rests on themolten metal located therein. Thus, the openings 3 and 5 provideseparate paths for the metal and slag, respectively.

It will be noted that the cross-sectional area of the chamber 55 in ahorizontal plane is much smaller than the cross-sectional area of thecupola in the same horizontal plane. Thus, if it should sometimes happenthat there is a variation in the pressure or depth of the slag in thechamber 55, this variation will have almost no effect on the depth ofthe slag bath within the cupola so that this depth will remain constantin accordance with the gas pressure prevailing in the cupola.

The chamber 55 is provided with a substantially central dividing wall 56located between the outlet spout 38 for the molten metal and the outletspout 6 for the slag. It will be noted from Figs. 4-6 that the dividingwall 56 is formed with an opening 32 located below the opening 3 at thelower side of inclined wall 36 to direct molten metal to the upwardlyextending opening 33 which communicates with the outlet spout 30.

The top of the chamber 55 is covered by a channel having thecross-section of an inverted U-shape and being provided with a frontopen end to provide a space 41 where the slag communicates with theouter atmosphere. The molten metal also communicates with the outeratmosphere at the spout 36. The front wall of the chamber 55 is providedwith a pair of openings 3| and 35 removably covered by a door 31 mountedon a front plate 46 which covers the entire front of the chamber 55except for the space 4| and a space 39 located just belowthe space 41.This space 39 is located opposite the opening 5 so that a rod insertedthrough the opening 36 may extend into the opening 5 to unplug the samewhen required. The opening 3! is aligned with the opening 3 to enablethe latter to be unplugged when required, and the opening 35 permits theentire chamber 55 to be drained. The top of the chamber is provided witha supporting surface '5 communicating through an opening with theinterior of the chamber, as is clearly shown in Fig. 4, so that an oilburner 51, or the like, may be mounted on this support I to heat slagwithin the chamber 55 so as to prevent setting thereof when the slag hasa high viscosity. The plate 40 may be removably mounted on the chamberby means of slots through which perforated lugs extend with pins locatedin these perforations to removably maintain the plate 46 in position, asis clearly shown at 58 in Fig. 2, for example. As is apparent from Fig.3, these pins are tapered so that the plate 40 may be tightly held inposition.

Thecupola is cooled. over itsv entire surface by a specialcooling means.This cooling means includes aperforatedpipe 60 located at the top of thecupola body about the same, as is shown in'Fig. 1, and communicatingwith any source of the cooling water so that this water may flow fromthe perforations in pipe 60 onto the outer surface of the cupola anddown the same. Located'about the cupola. body at the'level of the slagspent 6 and just beneaththetuyeres is a gutter 19 which receives thecooling waterflowing'downthe outer surface of the cupola from the pipe60. Apair of outlet pipes 20. and 2| are connected to the bottom wall ofgutter I9 and deliver water from the same. to a second gutter I6 locatedabout the cupolaat thebottomthereof. Just beneath the gutter I 9 thereis located a second. perforated pipe 28 which extends almost completelyabout the cupola, this'pipe being interrupted at the points where thechainber55 is joined tothe'cupola body. This pipe 28 may communicatewith the same source of fluid as thejpipe 60. The water'flowing fromperforated pipe 28 moves down theouter surface portion of the cupolalocated between the gutters l9 and I and is collected in the latter.

As is shown in Fig. 4, the gutter l9 extends aboutthe cupola bodybetweenthe same and the upper part of the chamber 55 so that the water in thegutter l9 cools the upper part of the chamber 55 aswell as the cupolaportion located adjacent thereto.

Asisshown most clearly in Fig. 5, the dividing wall 56 is provided witha space 42. As is shown most clearly in Fig. 2, a conduit 22communicates l withthe gutter l9 and has an open end located over thisspace 42 so that water from the gutter ID will be directed to this space42 to fillthe same and flow down the outer'surface of the chamber 55*. Aplate 29 extends in an inclined direction, 'as shown' in Figs. 2 and 3,from'the space 42 to the gutter IG so as to prevent water in gutter 16from splashing into the metal in outlet spout A special means isprovided, as shown in Figs.

3 and .8, for cooling the chamber 55 and cupola at the junctions betweenthe same. This means takes. the form of a pair of metal plates 25 andceiving chamber 55 so thatwater inthe gutter I9 will necessarily flowto'the narrow spaces be- "tween the plates 25 and 26 and these junctionsto providea veryefiective means forpositively cooling the 'latterso asto effectively prevent excessive strains and cracking at this usuallyweak pointin the cupola construction.

Fixedly mounted on a side wall of the chamber-55 is a box whichcommunicates with a pipe 8 to receive cooling water therefrom,thiscooling water for example being derived from the same source whichsupplies cooling water to the tuyeres. The box 9 is traversedby thebottom wall I! of the slag discharge spout 6, and the box- 9 is alsotraversed by an open top channel Ill having a bottom wall H" joined tothe boX 9 which is provided with an opening located between walls! I andH" to provide a free space into which watermay flow from the box 9 downthe channel It] along the floor it. Thus, slag the cupola. The pipe I4is also open on one. side thereofat the partwhere itcrosses the gutterl6, and the latter is provided with anextension l5 and channel .tlhaving an inclined bottom l8 and communicating with the interior of pipel4 so that the water from gutter It'which includesthe water from pipes20and 2| combines with thewater and. slagof channel H) in the pipe i i tomove down the pipe 14 to the collectionpit.

Thus, a very effective .means is provided for cooling'the entire outersurface of the cupola so as to prevent, as much as possible,deterioration of the lining I, and the location of the inner ends'of thetuyeres also contributes to this result, as explained above, so thatwith the? above described cupola the'deterioration of the refractorylining" I will be very greatly retarded and the slag composition willnot be contaminated .byithe material of the refractory lining. In thisway the composition of the slag maybe maintained constant in accordancewith the materials charged into the cupola.

The present invention is based on the known fact that if oneprogressively increases thenietallic. elements in the charge of agesproducer one obtains an apparatus which functions as acupola andproduces 'nietal'qas its principal productiand gas as its byproduct.

One of, the more important aims of the present invention is to i providea process and cupola which enablesan industrial foundry iron usableafter the first meltto be produced from scrap iron or a mixture of scrapwith old iron.

The characteristic fundamentals of the process of the present inventionare the following:

1.- The meltingtakes place in a reducing atmosphere.-

2. The droplets of metal" pass through a high temperature slagbath ofconstant depth and substantially constant? composition.

3; The furnace can operate eitheras a cupola or argas producer.

Each of these three points will now be separately described.

1. Melting in a. reducing atmosphere, that is to say inan atmospheresuch that the elements of the charge-such as silicon, iron and manganesedo not have a tendency to become oxidized.

According to the classical equations C+O2 CQ2+97.6 calories (1') CO2+C-200-383 calories (2) of carbon is utilized inthe charge of the cupola avery rapid manner.

with the excess coke according to Equation 2 to form carbon monoxide.The carbon monoxide forms a reducing atmosphere at very hightemperature. The metal oxides in the charge melt in this reducingatmosphere and are reduced while passing therethrough to form thecorresponding reduced metal.

The amount of carbon which is included in the charge of the cupolafurnace is such that there will always be an excess of carbon ascompared to the amount of oxygen which is introduced into the furnace.The factors which control the amount of excess are: the speed of flow ofair introduced into the cupola, the amount of air and the amount ofcarbon. According to the process of the present invention there isalways sufficient carbon in the cupola, to constitute an excess whencompared to the amount of oxygen that enters the cupola. This excess ofcarbon, coke being preferred because of its rich carbon content, is thebasis for the reducing atmosphere which is at all times present in thecupola.

The process of the present invention is not so much concerned with anefficient use of the combustible material as it is with the productionof a high quality metal, and therefore the aim is to produce a reducingatmosphere within the cupola while more or less neglecting the factor offuel consumption, since the principal purpose of the cupola is toproduce a cast iron which is of a high quality, and in order to producesuch a high quality cast iron an oxidizing atmosphere must at all timesbe avoided within the cupola. In order to obtain this reducingatmosphere, the fluid containing oxygen is introduced into the cupola ata relatively high temperature of between 400 to 600 C. This temperatureof the fluid may be obtained by reheating it before it passes throughthe tuyeres. Also the charge located within the furnace preferably has acarbon content of from to which is an ex- --cess in relation to thenormal requirements of the furnace. The fluid containing oxygen isintroduced into the cupola at a speed of from 80 to 100 meters persecond. The pressure of the fluid introduced into the cupola inaccordance with the present invention is much higher than the pressureused in conventional blast cupolas. In a cupola producing two tons ofmetal per hour, this pressure would be 60 cm. of water above atmosphericpressure as compared with cm. of water above atmospheric pressure usedin a conventional blast cupola.

The results produced by the above described process are that anessentially reducing atmosphere is obtained within the cupola due to thehigh percentage of carbon, the high heat of the fluid containing oxygenand the high speed with which this fluid is introduced. Also this highspeed of introduction of the oxygen-containing fluid results in the firebeing maintained within the cupola at about the center thereof, and theCO2 combines with the carbon to produce CO in At a few centimeters abovethe level of the tuyeres, the gas is composed almost entirely of CO. Asa result of the combustion of carbon into G0 a great amount of heat isproduced which is in the neighborhood of 2800 calories per kilogram ofcarbon and this great heat is utilized in the hot blast cupola to assurethe melting of the iron charge and the formation of slag. The extremelyhigh temperature within the cupola results in a relatively easyformation of slag which i free of iron oxide and which has between 1.4and 1.5 times as much CaO as S102. This slag is much less fusible thanslag produced in conventional cupolas. The resulting high temperature inthis central melting zone can easily reach a temperature of 1800 C. andcan be carried up to 2000 C. by the use of additional oxygen. Because ofthe relatively large dimension of the interior of the cupola withrespect to the cross-sectional area of the tuyeres, the gas within thecupola slowly rises and therefore leaves the cupola at the outletthereof at a relatively low temperature which is substantially below 700C. This gas which is produced in the cupola has a CO content which isabout seven times the CO2 content thereof.

The introduction of the heated air into the cupola at the relativelyhigh speed of -100 meters per second results in the creation of areducing atmosphere at a very high temperature, i. e. about 1800 C. inthe region where the air is introduced into the cupola. The hightemperature zone is concentrated about the zone of introduction ofheated air which is the fusion zone of the cupola.

Furthermore, it has been found that the introduction of the heated airinto the cupola at high speeds, namely 80-100 meters per second, resultsin a rapid .rise in temperature and yields a much faster reaction due tothe concentration of the hot reducing atmosphere about the reaction zoneof the cupola.

The introduction of heated air into the cupola at speeds substantiallybelow 80 meters per second results in a lower temperature than iproduced with the introduction of air at higher speeds, i. e. about 1600C. It has also been found that there is a great heat loss from aroundthe reaction zone in the cupola due to the heat radiation therefrom.Therefore, in such case, not only is the reaction zone at a lowertemperature but the high temperature is less concentrated and thereforethe temperature in the cupola at a distance above the reaction zone ishigher if the hot air is introduced slowly than is the case if the hotair is introduced rapidly.

For example, assuming the temperature in the zone of introduction of theheated air to be 1800 C. where the heated air is rapidly introduced at arate of 30-100 meters per second according to the present invention, thetemperature rapidly decreases above this zone so that at a relativelyshort distance therefrom the temperature in the cupola is relativelylow, i. e. about 800 C. If the heated air is introduced at a much slowerrate the temperature about the zone of introduction of the heated air islower, 1. e. about 1600 C., and at the same distance from this zone asin the above case, wherein the temperature in the eupola is down toabout 800 0., the temperature in the cupola at the same distance isstill quite high, 1. e. about 1500 C.

The amount-of'air required for the reaction is the'samewhether ornot'the'speed of introduction of air into the cupola is'rapidor slow.Therefore, if the speed of introduction of the heated air into thecupola is substantially below 80 meters per second, it is necessary toprovide the cupola with larger tuyres in order to allow for a sufiicientamount of air to enter the cupola.

It is thus possible by the rapid. introduction of rectly proportional tothe speed of the reaction.

The oxidation of the carbon, eitherdirectly to carbon monoxide or firstto. carbon dioxide. with subsequent reduction according to Equation 2above, to carbon monoxide, results in an overall exothermic processwhich raises the temperature in the cupola furnace to an extremelyhightemperature for such cupolas, namely 1550-1600 C. The high temperatureand the reducing atmosphere of the cupola result in the reduction of themetallic oxides to the corresponding reduced metals. The reducingatmosphere at high temperature also results in a reduction of themetallic sulfides by transfer of. the sulfide from theiron to, calciumor other similar metals. This shall be more clearly'explained later-Another extremely important advantage of the process of the presentinvention. is the maintaining of a slag bath having, constant'depthandsubstantially constant composition. Since the reduced metal passesthrough the slag bath where it reacts tobe further reduced and tocombine with other elements such as carbon to form alloys,theimportanceof maintaining a slag bath of constant depth andsubstantially constant composition is obviously great. If the depth ofthe slagbath and/or the..composition were to .vary

during the operation of the cupola furnace, the metal droplets whichpass therethrough. would not react uniformly and the productproducedwould therefore not haveuniform properties.

As explained elsewhere in the application, the

'depth of the slag bath is maintained constant by the use of the specialapparatus of the present invention. Further, the composition of the slagbath normally varies due to the melting and decomposition oftherefractory lining of the cupola furnace which mixes with theslagbath. The present invention by providing for cooling of the wall of thecupola'furnace during the operation of thesame prevents the melting anddecomposition of the refractory "lining and thereby prevents thecontamination ofthe slag bath withthe materials of the refractory. Thisresults ina slag bath of substantiallyconstant composition.

The composition of the slag bath is further maintained constant by 'theapparatusofthe 14 tureiofapproximately 500 C. issupplied through thetuyres, and thetuyres are;disposed.1in such away as to :add to thetemperature at their outlet ends so as to: thus produce the endothermicReaction. 2.. The gas producing zone can be. considered as the gasproducing zone of a gasproducercooled by the molten metal, which passesfromthe' top tothebottom. Th metal meltsin a reducing atmosphere ofcarbo'nmonoxide, and it moves'downwardly in the form of droplets and theEco, which has for-example been charged in the form of rust and which isdissolved into'the iron, is reduced in passing through this superheatedreducing zone.

The iron,,in the proportion that it .is melted; absorbs carbon which isnot burned, in passing the tuyeres; i

It is a well known fact that at a temperature of 1803 (3., oxygen has amuch greateraflinity for carbon than for silicon so that at this tem'peratureit :is absolutelyimpossible for silicon to unite with oxygen andbecome silica. On the contrary, the reverse takes place, and the silicain the charge is reduced tosilicon by the carbon or. CO. With theprocessof the present invention it is possible to obtain. 2.5% silicon at theoutlet of the cupola when the original charge contained 2.2% silicon.

Even if the scrap iron charged is very. highly oxidized, the FeO contentof the slag obtained never exceeds 0.8% which shows that the slag nevercontains all of the iron content ofthe ashes in the coke charged.

In a classicalcupola, the attemptisalways to burn as much carbon aspossible into CO2, which prevents working in a very high temperature,with the result that the condition -are those that produce a zone wheresilicon, manganese and iron are necessarily oxidized.

Melting in a reducting atmosphere according to the present inventionproduces moreover two additional advantages:

(a) No metallicelementsare lost to the slag. H.Jungbluthhas establishedthat the loss of ironin a cupola is proportionaltothe ratio of With thepresent invention this ratio isveryrlow, and this has'an importanteconomical advantage if one considers that thoseelements which aremosteasily oxidized obviously are those whose reduction is mostdifficult, and as a consequence these elements are the costliest sincethey require an extremelyhigh gross weight to'produce 1000 he. of usefulmetal in the furnace.

(b) The composition of slag is not. as in the conventional cupola,modified by the oxidized elements in the zonecf fusion in a way whichcannot be controlled. It is known that ina conventional apparatus, wherethe Zone of fusion is oxidizing, numerous uncontrollable factorsintervene in the process, such as pressureand hulayer of slag whosecomposition and thickness is constant and whose temperature is veryhigh.-

It is relatively unimportant that an equilibrium of reaction cannot takeplace because of the small length of time during which the droplets ofmetal pass through the slag. Substantially the same result can beobtained if constant controllable reactions can be produced during thetime that the molten metal droplets pass through the slag, and so it issufficient if the layer of slag has a constant thickness. As a result ofthis feature, which is obtained by continuous drawing off" of the slagfrom the furnace as it is being produced therein, it is possible tomaintain in the interior of the furnace a slag having a thickness of theorder of 300 mm., whereas with a conventional cupola one can besatisfied with an extremely simple device since the only objective is toprovide a mechanical separation of metal from slag.

In order to maintain the composition of the slag constant, i necessaryto avoid contamination of the slag with the material of the refractorylining, and this is done by the above-described very efficient coolingof the wall of the furnace as well as by extending the tuyeres to apoint within the furnace which is beyond the inner surface thereof sothat the combustion area defined by the outlet ends of the tuyeres islocated away from the inner lining of the furnace. It is true that thisstrong cooling of the furnace is very costly in calories, but from ametallurgical point of view it is indispensable if the operator is to bethe master of the composition of the slag.

Finally, the high temperature which obtains in the gasification zonegives the slag a very high temperature.

According to known principles it is most desirable that the molten metalhave the greatest opportunity to react with the slag in order thatdesirable elements in the slag may be absorbed into the metal andundesirable elements may be absorbed into the slag. The degree to whichthese desirable reactions take plac increases with an increase intemperature, and according to the present invention the cupola operatesat a very high temperature. The degree to which these reactions takeplace also increases with an increase in the surface contact between themetal and slag, and ii a comparison is made between the cupola of thepresent invention and a hearth furnace such as the Martin furnace, or anelectric furnace, it will be seen that process of the For 100 caloriesof coke:

26.5 are used to produce molten metal, 54 are expended in the form of agas which may be used for various purposes, 1.5 are lost to the slag,10.5 are lost to the cooling water, and 7 .5 are lost in reheating thecombustion air.

'It is thus possible to combine into the single apparatus of the presentinvention two devices: a cupola which utilizes kgs. of coke of 7000calories to melt a ton of metal and a gas producer which gasiiies at thesame time, without loss, 9.5 lcgs. of the same combustible material.

The reduced gas is produced at the rate of kg. per ton of metal for acharge which carries 1'70 kg. This gas contains 24% CO and 4% CO2.

As a comparison there is shown herewith a table of the different typesof charges necessary to produce the same metal with the new process andwith a conventional cupola.

7 Conventional New Cupola Cup 013 (a) metallic charge: Percent PercentOld Iron 35 c Iron Alloys at 2 The excessive consumption of combustiblematerial in the new cupola under normal circumstances is evident fromthis table, but this excessive consumption is largely compensated by thefact that the conventional cupola requires frequent interruptions forrepairs, etc. The quantities of combustible material necessary forfusion vary between the following limits:

11% of coke having 10% of ashes with a charge of 100% pig iron; and

24% of coke having 10% of ashes with a charge of 100% scrap steel.

For these charges it is necessary to provide about 1000 cubic meters ofair for each ton of molten metal.

With the apparatus and process of the present invention, when themelting of metal is interrupted the cupola can continue to function as agas producer. After an interruption of eight hours it is necessary tocharge 300450 kgs. of coke to resume melting of metal; after aninterruption of 30 hours 600-700 kgs. of coke would be required.

Experience has shown cupolas according to the present invention can beconstructed for any desired production capacity, i. e. 5-20 tons perhour and more.

By way of example the constructive characteristics of a new cupolahaving a capacity of 5 tons per hour are the following:

Its capacity is in the neighborhood of 5 tons per hour; the diameterbetween tuyeres is about 850 mm.; its exterior is cooled by waterflowing down the same; the tuyres are independently cooled; the top isclosed; 35% of the gas is sent to an air reheater, the rest being usedfor other needs of the foundry.

The air is reheated by passage through three phases of exteriorly heatedtubes, this heating being done by the combustion of gas from the cupola.A filter is placed between the cupola and air reheater to retain thelarger impurities in the air.

A comparison of the cupola furnace and the process of the presentinvention as compared to the known cupola furnaces shows the following:

- Hot air cupola Normal cold an u Gupola according to cupcla ga f ggi figx ggg? the present invention Coke ashes) 100 kg. (10% ashes) 60-80 kg.ashes) 200 kg. Carbon per ton of metal 80 kg l. 65 kg 180 kg. Slag perton of metal 130 kg. Gas Produced:

(1) CO; 23%. (2) O2 (3) CO 2930%. Calories SOD-1,000 kcal. Temperatureof slag l 1,5501,600 0. Analysis of slag:

SiO 30%. (2) CaO 50%. (3) Foo. 03. Working l extremely reductive. Carbonor schist 50 kg. having 70% ashes. Limestone. 130 kg. New pig iron Oldpig iron FeSi (10%) Scrap iron 1,000 kg.

The technical possibilities of a cupola according to the invention are:

It is possible to obtain a metal having properties very different fromthose which are charged because the latter after melting pass in areducing atmosphere of very high temperature and then into an abundantslag which also has a very high temperature.

Moreover, the only constituents in the slag are obtained from the chargeat the top of the furnace. The slag is not contaminated by the elementsof the refractory lining. The height of the slag, as well as otherfactors, are maintained constant to produce internal equilibrium in theapparatus.

It is possible to obtain slags which have a low degree of fluidity andwhich at the temperatures of conventional cupolas would result instoppage of passageways and would be impossible to empty.

As a result to these characteristics it is possible to carry out aseries of metallurgical operations which produce a final metal productwhose analysis depends on the composition of the slag' which intervenesin accordance with the laws of chemical equilibrium.

By way of example, it is possible also (a) To obtain a hematite metal oflow sulfur from scrap steel;

(b) To obtain highly carbonized metal from a slightly carburized charge;

(0) To obtain a metal which is highly resistant to the heat or wearwhich could up to the present time be obtained only from an electricfurnace;

(d) To obtain products of different types from the same charges or froma series of different charges by combining various materials with themetal leaving the cupola, this combination being very easy because ofthe high temperature of the metal as it leaves the cupola.

The apparatus of the present invention is distinguished from theapparatus of conventional hot blast cupolas, in that in the latter thereis a constant striving to obtain two objects:

(a) Diminution of coke consumption, and

(b) The use of coke of poor quality.

In accordance with the present invention the operations take place (a)At extremely high temperatures and in a highly concentrated zone offusion,

(b) In a highly reducing atmosphere.

Whatever metal is obtained with the process and apparatus of the presentinvention, it distinguishes from metals made from other apparatus by theslag of the present invention than in the ashes of combustion.

The charge used in the process and apparatus of the present inventioncan include oxidized metals. By varying the temperatures of the airintroduced into the cupola and by varying the quantity and quality ofcombustible material and the quantity and composition of the slag, onecan voluntarily control the carbon content of the metal produced. It isthus possible to produce a metal having 3.4% of carbon from a charge of106% steel, and one can also produce a slightly carbonized metal from ahighly carbonized charge.

The phosphorus introduced in the form of phosphorized scrap metal or inthe form of phosphates passes completely into the molten metal.

The silicon can be introduced in the form of ferro-silicon or oldsilicious iron.

In a case where there is little silicon introduced in the charge, it ispossible to find all of the silicon of the charge in the metal produced.

The sulfur content can be greatly reduced by controlling the slag.

On the subject of sulfur content, an example is given herewith of theapplication of the new apparatus to the production of a de-sulfurizedproduct.

Sir Charles Goodeve and J. Pearson have recently written that in orderto free iron from $111 fur it is necessary to place it in intimatecontact with a phase in which the sulfur potential is of a low value andwhich besides possesses a sufiioient absorption capacity; moreover onecan lower the sulfur potential by a phase which dissolves sulfur and iscomposed of an appropriate solvent added to other elements such as thealumino-sili cates of calcium which are the least expensive goodsolvents.

The de-sulfurizing equations can be described as We have seen that thebasic principle of the invention is to melt in a reducing. atmosphere.The cited authors emphasize that the capacity of a basic slag can be onehundred times greater or advantageous with respect to sulfur in a blastfurnace than the same slag under the oxidizing conditions which areproduced in a Martin furnace, for example. The atmosphere in the cupolaof the present invention closely approaches that of a blast furnace. R.Rocca, N. J. Grant, and J Chipman have all demonstrated that the degreeto which de-sulfurizing takes place will be in creased as the quantityof FeO in the slag is decreased.

The amount of FeO in the slag obtained in the present invention is muchlower than the critical content of 2 cited by the above authoritiessince in the slag of the present invention where the apparatus andprocess is practiced industrially, the FeO content never exceeds 0.8%.It is interesting to note that it is the extremely high FeO content inthe slag of conventional cupolas which prevents success in. thede-sulfurizing by calcium carbide.

One might think that the two necessary conditions of goodde-sulfurizing, that is, the basic slag and a reducing atmosphere, areindependent of each other. This is not the case. In effect, in anoxidizing atmosphere, the basic slag is acidifled by the silica producedfrom the oxidation of the silicon in the charge.

Equation 5 shows that carbon is necessary to eliminate the FeO producedby Reaction 4. In a reducing atmosphere and at a high temperature themolten metal becomes rapidly saturated with carbon and as a result ofthe present invention this latter element is present in a sufficientquantity in each droplet of metal to assure the displacement ofequilibrium to the right.

. With the process of the present invention the reactions between themetal and slag take place, with respect to de-sulfurization, under veryfavorable circumstances as much with respect to temperature as withrespect to surface contact.

E. Whitten has indicated the importance of high temperature inde-sulfurization. A high temperature promotes separation of sulfur fromiron.

Finally, G. Derge, W. O. Philbrook and Kenneth M. Goldman have shownthat the speed with which this separation takes place depends to a greatmeasure on the surface of contact between metal and slag, and it hasbeen shown that this surface is at least one hundred times greater in acupola than in a crucible or electric furnace.

Finally there is presented herewith data relative to a normal process ina cupola of the present invention.

Silicon charged 2. 2. 37% 2. 32% 2. 14%

Analysis of Metal:

ilioon percent 2. 35 2. 43 2. 31 2. 13 manganese d 0.42 0. 56 0.46 0. 50phosphorus. 0.84 0.61 0.78 0.55 carbon (total) 3. 455 3. 59 3. 59 3. 63sulfur 10.... 0. 083 0. 05 0. 058 0. 067 Temperature of the melt C 1,550 l, 524 l, 51- 1,516 Analysis of slag:

SiOz .lpercentn 39.8 34 37.05 35.3 d 43. 7 44, 9 46. 9 44.1

12. 2 15. 87 10. 76 15.17 0. 707 0. 82 0. 73 0. 74 0.801 0. 45 0.86 0.762. 295 3. 69 2. 93 3. 44 S do. 1.02 1.64 1.32 1.48 Temperature of theair. 0.. 480 502 549 483 Pressure of the air (mm. of water aboveatmosphere) 754 720 755 758 Temperature of Gas at the top outlet 334 393372 372 PROPERTIES or METAL OBTAINED The molten metal obtained directlyfrom the cupola is very hot (over 1500 C.) and fora metal of the samecomposition and temperature producedby an ordinary cupola, it hassuperior flowing qualities and a lesser propensity to tempering and itis possible to very easily combine this metal with other elementsinserted into the molten metal.

(a) Iron for centrifugal cast pipes To-produce this type of iron in aconventional cupola one cannot include steel in the chargeif one wishesto avoid reheating of the pipe, and besides one cannot use less than 60%of pig iron.

With the present invention however this same iron can be produced from acharge having only scrap steel and iron.

(b) Iron having high. mechanical resistance For this iron the standardcharge has the fob lowing composition:

which corresponds to a chemical composition of molten metal:

, Per cent o 2.8 to 3.2 s1 i 1.8 to 2.3 Mn 0.5 to 0.8 I P 0.05 to 0.1 s0.05 to 0.08

MECHANICAL CHARACTERISTIC OF IRON HAVING A HIGH MECHANICAL RESISTANCEFrom a 100% steel and iron alloy charge and after combining the moltenproduct with 0.2% of silicocalcium and 0.5% of calcichrome, there isproduced a product having a resistance to bending of 56.6 kgs./cm. for adeflection of. 9 mm. in a bar 300 mm. long and having a diameter of0.600 mm. between supports Resistance to traction: 42.1 kgs.-/cm'.

From 80-85% steel and iron alloy there is produced a shear resistance of30 l0'kgs./cm.

The Brinell hardness varies in eneral from 190 to 250 according to thecontent of carbon and'silicon in the molten metal. Thehardness varieslittle over a given thickness.

An examination of a micrograph before etching.

shows a very fine graphite uniformly distributed. After etching it maybe seen that the texture is essentially perlitic.

(c) Refractory iron (high resistance to heat) An iron produced from 100%steel and ferro silicon and to which 0.8% of Cr has beenadded in themolten product, can be used without risk of expansion up to 800 C.

It will be understood'that each of the elements described above, or twoor more together, may also find a useful application in other types ofcupola furnace and process for operating the same differing from thetypes described above;

What is claimed as new and desired to be secured by LettersPatent is: 1.A cupola furnace, comprising, in combination, an elongated hollow bodyhaving a vertical,

21 central axis; a closed top and a bottom wall toward which moltenmetal andslag move, said hollow body having an inner refractory liningand having a side wall portion adjacent said bottom wall thereof formedwith a pair of openings, one of which passes through said side wallportion substantially at the level of said bottom wall to lead moltenmetal from said hollow body and the other of which passes through saidside wall portion above said one opening to lead slag from said hollowbody; a receiving chamber connected to said hollow body at said sidewall portion thereof and communicating with said openings, saidreceiving chamber having a slag discharge spout and a metal dischargespout located below said slag discharge spout and said receiving chamberhaving a cross-sectional area in a horizontal plane which issubstantially smaller than the cross-sectional area of the interior ofsaid hollow body in the same horizontal plane, said receiving chamberalso having a dividing wall extending beneath said one opening and beinglocated between said spouts to separate molten metal and slag from eachother; gas outlet valve means located adjacent said top of said hollowbody to maintain therein a slag bath of constant depth; and coolingmeans associated with the outer surface of said hollow body for coolingthe same over substantially the entire outer surface thereof.

2. A cupola furnace, comprising, in combination, an elongated hollowbody having a vertical central axis, a closed top and a bottom walltoward which molten metal and slag move, said hollow body having aninner refractory lining and having a side wall portion adjacent saidbottom wall thereof formed with a pair of openings, one of which passesthrough said side wall portion substantially at the level of said bottomwall to lead molten metal from said hollow body and the other of whichpasses through said side wall portion above said one opening to leadslag from said hollow body; a receiving chamber connected to said hollowbody at said side wall portion thereof and communicating with saidopenings, said receiving chamber having a slag discharge spout and ametal discharge spout located below said slag discharge spout and saidreceiving chamber having a cross-sectional area in a horizontal planewhich is substantially smaller than the cross-sectional area of theinterior of said hollow body in the same horizontal plane, saidreceiving chamber also having a dividing wall extending beneath said oneopening and being located between said spouts to separate molten metaland slag from each other; gas outlet valve means located adjacent saidtop of said hollow body to maintain therein a slag bath of constantdepth; cooling means associated with the outer surface of said hollowbody for cooling the same over substantially the entire outer surfacethereof; and a plurality of tuyeres mounted on said hollow body in ahorizontal plane substantially at the level of said discharge spout.

3. A cupola furnace, comprising, in combination, an elongated hollowbody having a vertical central axis, a closed top and a bottom walltoward which molten metal and slag move, said hollow body having aninner refractory lining and having a side wall portion adjacent saidbottom wall thereof formed with a pair of openings, one of which passesthrough said side wall portion substantially at the level of said bottomwall to lead molten metal from said hollow body and the other of whichpasses through'said side than the cross-sectional area of the interiorof.

said hollow body in. the same horizontal plane,

said receiving chamber also having a dividing wall extending beneathsaid one opening and being located between said spouts to separatemolten metal and slag from each other; gas

outlet valve means located adjacent said top of said hollow body tomaintain therein a slag bath of constant depth; cooling means associatedwith the outer surface of said hollow body for cooling the same oversubstantially the entire outer surface thereof; and a plurality oftuyeres mounted on said hollow body in a horizontal plane substantiallyat the level of said discharge spout, said tuy-eres extending into saidhollow body beyond said inner refractory lining thereof to provide acombustion area in the horizontal plane of said tuyeres which is spacedfrom said refractory lining.

4. A cupola furnace, comprising, in combinaj tion, an elongated hollowbody having a vertical;

central axis, a closed top and a bottom wall toward which molten metaland slag move, said hollow body having an inner refractory lining andhaving a side wall portion adjacent said bottom wall thereof formed witha pair of openings, one of which passes through said side wall portionsubstantially at the level of said bottom wall to lead molten metal fromsaid hollow body and the other of which passes through said side wallportion above said one opening to lead slag from said hollow body; areceiving chamber connected to said hollow body at said side wallportion thereof and communicating with said openings, said receivingchamber having a slag discharge spout and a metal discharge spoutlocated below said slag discharge spout and said receiving chamberhaving a cross-sectional area in a horizontal plane which issubstantially smaller than the cross-sectional area of the interior ofsaid hollow body in the same horizontal plane, said receiving chamberalso having a dividing Wall extending beneath said one opening and beinglocated between said spouts to separate molten metal and slag from eachother; gas outlet valve means located adjacent said top of said hollowbody to maintain therein a slag bath of constant depth; cooling meansassociated with the, outer surface of said hollow body for cooling thesame over substantially the entire outer surface thereof; and aplurality of tuyercs mounted on said hollow body in a horizontal planesubstantially at the level of said discharge spout, said tuyresextending into said hollow body beyond said inner refractory liningthereof to provide a combustion area in the horizontal plane of saidtuyres which is spaced from said refractory lining, and said tuyeresbeing adjustably mounted on said hollow body for movement toward andaway from said central axis thereof so that the size of said combustionarea may be varied.

5. A cupola furnace, comprising, in combination, an elongated hollowbody having a vertical central axis, a closed top and a bottom walltoward which: molten metal and slagmove, said 3 and the other of whichpasses through said side wall portion above said one opening to.leadslag from said hollowbody; a receivingchamber'connected to saidhollow body at said side. wall'portion thereof and'communicating withsaidlopenings, said receiving chamber having a slag discharge spoutand'a metal discharge'spout'located below said slag discharge spout ands-aidreceiwing chamber havingv a cross-sectional area in a horizontallane which is substantially" smaller than the cross-sectional area oftheinterior of said. hollow body in the same horizontal plane,

said receiving chamber also. having a dividing wall extendingbeneathsaid one opening and-fibeing located between said spouts toseparate molten metal and slag from each other; gas outlet valve meanslocated adjacent said top of said hollow body to maintaint-herein a slagbath of constant depth; cooling means associated withv the outer surfaceof said hollow body for cooling thesamev over substantially the entireouter surface thereof; and a plurality of tuyeres mountedon said. hollowbody in a horizontal plane substantially at the level of said dischargespout, said tuyeres being hollow so that they may be cooled by a coolingfluid located therein.

6. A cupola furnace, comprising, in combination, an elongatedhollow bodyhaving a vertical central axis, a closed top-and a bottom wall towardwhich molten metal and slag move, said hollow body having an innerrefractory lining and having a side wall portion adjacent said bottomwall thereof formed with a pair: of openings, one of which passesthrough said side wall portion substantially at the level of said bottomwall to lead molten metal from said hollow body and the other of whichpasses through said side wall portion above said one opening to leadslag from said hollow body, said one opening being substantiallyhorizontal and said other opening being inclined upwardly from theinterior ofsaid' hollow body; a receiving chamber connected to saidhollow body at said side wall portion thereof and communicating withsaid openings, saidreceiving chamber having a slag discharge spout and ametal discharge spout located below said slag discharge spout and saidreceiving chamber having a cross-sectional area in a horizontal planewhich is substantially smaller than the cross-sectional area of theinterior of said hollow body in the same horizontal plane, saidreceiving chamber also having a dividing wallextending beneath said oneopening and-being located between said spouts to separate molten metaland slag from each other; gas outlet'valve means located adjacent saidtop of said hollow' wall'tolead molten metal from saidvhollow body andthe other of which passes through said side wall'portion'above said oneopening to lead slag from said hollow body, said bottom wall being.inclined downwardly from said one opening and said hollow body beingformed with an additional openingv passing through the side wall thereofand communicating with the lowermost part of said inclined bottom'wall;a receiving chamber connected to said hollow body at said side wallportion thereof and communicating with said openings, said receivingchamber having aslag discharge spout and a metal discharge spout locatedbelow said slag discharge spout and said receiving chamber having across-sectional area in a horizontal plane which is substantiallysmaller than the cross-sectional area of the interior of said hollowbody in the same horizontal plane, said receiving chamber also having, adividingwall extending beneath said one opening.

and'being located between said spouts to separate molten metal and slagfrom each other; gas outlet valve means located adjacent said top ofsaid hollow body to maintain therein a slag bath of constant depth; andcooling means associated with the outerv surface of said hollow body forcooling the same over substantially the entirewall to lead molten metalfrom said hollow body andv the other of which passes through said sidewall portion above said one opening to lead slag from said hollow body,said bottom wall being inclined downwardly from said one opening andsaidhollow body being formed with an additional substantially horizontalopening passing through the side wall thereof and communicating with thelowermost part of said inclinedbottom wall; a receiving chamberconnected to said hollow body at said side wall portion thereofandcommunicating with said openings, said receiving chamber having a slagdischarge spout and a metal discharge spout located below said slagdischarge spout and said receiving chamber having a, cross-sectionalarea in a horizontal plane which is substantially smaller thanthecross-sectional. area of the interior of said hollow body in the samehorizontal plane, said receiving chamber also having a dividing wallextending beneath said one opening and being located between said spoutsto separate molten metal and. slag fromeachotherigas outlet valve meanslocated adjacent said top of said hollow body to maintain therein a slagbath of constant depth; and cooling: means associated with the outersurface of said hollow body for cooling the same over substantially theentire surface thereof.

9; A. cupola furnace, comprising, in combination, an elongated hollowbody having a vertical central axis, a closed top and a bottom walltowardwhich molten metal andslag move, said hollow body having an innerrefractory lining and having a side wall portion adjacent said bottomwall thereof formed with a" pair of openings, one of which passesthrough said side wall portion substantially at the level of said bottomwall to lead molten metal from said hollow body and the other of whichpasses through said side wall portion above said one, opening to leadslag from said hollow body; a receiving chamber connected to said hollowbody at said side wall portion thereof and communicating with saidopenings, said receiving chamber having a slag discharge spout and ametal discharge spout located below said slag discharge spout and saidreceiving chamber having a cross-sectional area in a horizontal planewhich is substantially smaller than the cross-sectional area of theinterior of said hollow body in the same horizontal plane, saidreceiving chamber also having a dividing wall extending beneath said oneopening and being located between said spouts to separate molten metaland slag from each other; gas outlet valve means located adjacent saidtop of said hollow body to maintain therein a sla bath of constantdepth; cooling means associated with the outer surface of said hollowbody for cooling the same over substantially the entire surface thereof;and support means located on said chamber adjacent an upper part thereofto support a heater for heating slag in said receiving chamber so as toprevent setting of slag in said receiving chamber.

10. A cupola furnace as defined in claim 2 and wherein said coolingmeans comprises a first perforated pipe located about said hollow bodyadjacent the top thereof for spraying cooling water on the outer surfaceof said hollow body, a first gutter located about said hollow bodysubstantially at the level of said tuyeres for receiving cooling waterfrom said first pipe, a second perforated pipe located about said cupolajust beneath said first gutter for spraying cooling water on said cupolabelow said first gutter, a conduit communicating with said first gutterand having an open end located adjacent said 26 receiving chamber forguiding cooling water from said first gutter onto said chamber, and asecond gutter located about said cupola at the bottom thereof forreceiving cooling water from said conduit and second perforated pipe.

11. A cupola furnace as defined in claim 10 and wherein metal plates aremounted close to the outer surface of said hollow body respectively atthe junctions thereof with said receiving chamber and wherein said firstgutter is formed with slits located over said metal plates between thesame and said hollow body and conforming to the shape thereof to directliquid from said first gutter onto said hollow body between the same andsaid metal plates so as to cool said hollow body and receiving chamberat said junctions.

12. A cupola as defined in claim 1 and wherein said receiving chamber isformed with a pair of passages respectively aligned with said openingsto permit rods to be inserted through said passages to said openings tounplug the same.

ROBERT DOAT.

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